I really don't think you have anything to worry about. The plastic these little guys eat needs to be partially degraded and broken up into smaller pieces for them to make any meaningful digestive progress. It's exceedingly unlikely the bacteria themselves are going to get efficient enough that your non-waste plastic stuff is in any danger. More likely, the enzymes themselves will be used as part of a larger controlled industrial process (enzyme recapture is important to staying cost effective after all). Even if that wasn't the case, these bacteria are suited for life in a landfill, not in your pipes.